Dielectric ceramic and laminated ceramic capacitor

ABSTRACT

A dielectric ceramic which is capable of achieving a laminated ceramic capacitor with high reliability, in particular, favorable lifetime characteristics in a load test, even when a dielectric ceramic layer is reduced in thickness, contains one of Ba(Ti, Mn)O 3  and (Ba, Ca)(Ti, Mn)O 3  as a main component, and R (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and/or Y), M (Fe, Co, V, W, Cr, Mo, Cu, Al, and/or Mg) and Si as accessory components. The area of a region in which at least one of R and M is present is 10% or less on average on a cross section of each main component grain.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a dielectric ceramic and a laminated ceramiccapacitor, and more particularly, relates to a dielectric ceramicsuitable for use in a thin-layer high-capacity laminated ceramiccapacitor, and to a laminated ceramic capacitor made using thedielectric ceramic.

2. Description of the Related Art

As one of effective means for satisfying the needs for size reductionand higher capacity in laminated ceramic capacitors, the dielectricceramic layers provided in the laminated ceramic capacitors aresometimes reduced in thickness. However, as the dielectric ceramiclayers become thinner and thinner, the electric field intensity perdielectric ceramic layer is increased. Therefore, a higher reliability,in particular, a higher lifetime characteristics in a load test isrequired for the dielectric ceramic used.

BaTiO₃ based dielectric ceramics are often used as the dielectricceramics constituting dielectric ceramic layers of laminated ceramiccapacitors. In order to improve the reliability and various electricproperties of the BaTiO₃ based dielectric ceramics, elements such asrare-earth elements and Mn have been added as accessory components.

For example, Japanese Patent Application Laid-Open No. 10-330160 (PatentDocument 1) discloses, for the purpose of improving the dielectricbreakdown voltage, a dielectric ceramic which has a core-shell structureand contains ABO₃ (A always contains Ba, and may further contain atleast one of Ca and Sr, while B always contains Ti, and may furthercontain at least one of Zr, Sc, Y, Gd, Dy, Ho, Er, Yb, Tb, Tm, and Lu)as its main component, and in the dielectric ceramic, at least one ofMn, V, Cr, Co, Ni, Fr, Nb, Mo, Ta, and W is substantially homogeneouslydistributed through the grains. In addition, Patent Document 1 disclosesan example in which Mg is used as a shell component and Mg isdistributed only in the shell portion, but not in the core.

However, even when the dielectric ceramic described in Patent Document 1mentioned above is used, the reliability, and in particular, thelifetime characteristics in a load test, may be insufficient as thedielectric ceramic layers are further reduced in thickness, andtherefore, further improvements have been desired.

SUMMARY OF THE INVENTION

Thus, some of the objects of the present invention is to provide adielectric ceramic which is capable of achieving high reliability evenwhen the dielectric ceramic layer is reduced in thickness, and toprovide a laminated ceramic capacitor made with the dielectric ceramic.

The present invention is first directed to a dielectric ceramiccontaining one of Ba(Ti, Mn)O₃ and (Ba, Ca) (Ti, Mn)O₃ as a maincomponent; and R (R is at least one selected from La, Ce, Pr, Nd, Sm,Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y), M (M is at least oneselected from Fe, Co, V, W, Cr, Mo, Cu, Al, and Mg), and Si as accessorycomponents. In order to solve the above-mentioned technical problem, thedielectric ceramic of the invention has a feature that the ratio of thearea of a region in which at least one of R and M is present is 10% orless on average on a cross section of each main component grain.

In a dielectric ceramic according to the present invention, the Mncontent ratio is preferably 0.01 to 1 mol % with respect to all of (Ti,Mn) sites.

The Ca content ratio is preferably 15 mol % or less with respect to allof (Ba, Ca) sites.

The present invention is also directed to a laminated ceramic capacitorincluding a capacitor main body including a plurality of stackeddielectric ceramic layers and a plurality of internal electrodes formedalong specific interfaces between the dielectric ceramic layers; and aplurality of external electrodes formed in positions different from eachother on an external surface of the capacitor main body and electricallyconnected to specific one of the internal electrodes.

The laminated ceramic capacitor according to the invention has a featurethat the dielectric ceramic layers are composed of the dielectricceramic according to the invention.

In the dielectric ceramic according to the invention, Mn is presenthomogeneously as a solid solution in the main component grains, therebyimproving the insulating property in the main component grains. In thiscase, the ratio of the solid solution region with the R component and/orM accessory components therein is 10% or less, and local grain growthcan thus be suppressed on firing. Therefore, when a laminated ceramiccapacitor is constructed with the use of the dielectric ceramicaccording to the invention, the fired dielectric ceramic layers can bemade smoother. This is advantageous for a reduction in the thickness ofthe laminated ceramic capacitor, and high reliability, in particular,favorable lifetime characteristics in a load test can be maintained evenin the thinned laminated ceramic capacitor.

No local grain growth is caused when Mn only is present homogeneously asa solid solution in the main component grains. However, it is believedthat the local grain growth is likely to be caused when Mn is presenthomogeneously as a solid solution in the main component grains, and Rand/or M is/are present in the main component grains. In this regard,when the ratio of the solid solution region with the R component and/orM component therein is 10% or less, it is expected that local graingrowth may be suppressed.

In the dielectric ceramic according to the invention, when the maincomponent is (Ba, Ca)(Ti, Mn)O₃, that is, when Ca is present as a solidsolution at Ba sites, the action of suppressing the local grain growthis further enhanced, and the reliability is further improved.

In the dielectric ceramic according to the invention, the lifetimecharacteristics can be further improved when the Mn content ratio is0.01 to 1 mol % with respect to all of (Ti, Mn) sites.

In addition, when the Ca content ratio is 15 mol % or less with respectto all of (Ba, Ca) sites in the dielectric ceramic according to theinvention, the lifetime characteristics can be further improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view schematically illustrating a laminatedceramic capacitor 1 composed with the use of a dielectric ceramicaccording to the invention; and

FIG. 2 is a cross sectional view schematically illustrating maincomponent grains 11 of a dielectric ceramic according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, a laminated ceramic capacitor 1 with adielectric ceramic according to the invention applied will be describedfirst.

The laminated ceramic capacitor 1 includes a capacitor main body 5composed of a plurality of stacked dielectric ceramic layers 2 and of aplurality of internal electrodes 3 and 4 formed along interfaces betweenthe dielectric ceramic layers 2. The internal electrodes 3 and 4 maycontain, for example, Ni as their main component.

First and second external electrodes 6 and 7 are formed in positionsdifferent from each other on an external surface of the capacitor mainbody 5. The external electrodes 6 and 7 may contain, for example, Ag orCu as their main component. In the laminated ceramic capacitor 1 shownin FIG. 1, the first and second external electrodes 6 and 7 are formedon end surfaces of the capacitor main body 5 opposed to each other. Asfor the internal electrodes 3 and 4, the plurality of internalelectrodes 3 and the plurality of internal electrodes 4 are electricallyconnected respectively to the first external electrode 6 and the secondexternal electrode 7, and the first and second internal electrodes 3 and4 are arranged alternately with respect to the stacking direction.

It is to be noted that the laminated ceramic capacitor 1 may be atwo-terminal laminated ceramic capacitor provided with the two externalelectrodes 6 and 7, or may be a multi-terminal laminated ceramiccapacitor provided with a number of external electrodes.

In this laminated ceramic capacitor 1, the dielectric ceramic layers 2are composed of a dielectric ceramic containing a Ba (Ti, Mn)O₃ or (Ba,Ca) (Ti, Mn)O₃ as its main component, and R (R is at least one selectedfrom La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y), M(M is at least one selected from Fe, Co, V, W, Cr, Mo, Cu, Al, and Mg)and Si as accessory components.

FIG. 2 shows a cross sectional schematic view of main component grains11 of the dielectric ceramic. Referring to FIG. 2, Mn is presenthomogeneously as a solid solution in most regions of the main componentgrains 11 as described above. On the other hand, R and M are not presentas a solid solution in the main component grains 11. More specifically,the region in which at least one of R and M is present (hereinafter,referred to as an “R/M region”) 12 is formed on the surface portion ofthe main component grains 11. However, the R/M region 12 is notsufficient to form a thin shell in a concentric fashion with the maincomponent grains 11. Therefore, the main component grains 11 are notadapted to constitute a core-shell structure, unlike the case of thedielectric ceramic described in Patent Document 1 mentioned above.

The dielectric ceramic constituting the dielectric ceramic layers 2 hasa feature that the average ratio of the area of the R/M region 12 on across section of each main component grain 11 is 10% or less.

Mn is present homogeneously as a solid solution in the main componentgrains of the dielectric ceramic, thereby allowing the insulationproperties in the main component grains 11 to be improved. In this case,the ratio of the area of the R/M region 12 on a cross section of themain component grain 11 is only 10% or less, thus allowing local graingrowth to be suppressed on firing. Therefore, even when the laminatedceramic capacitor is reduced in thickness, high reliability can beachieved, and in particular, favorable lifetime characteristics in aload test can be achieved.

When the content ratio of Mn is 0.01 to 1 mol % with respect to all of(Ti, Mn) sites, the lifetime characteristic can be further improved.

In addition, when the dielectric ceramic contains (Ba, Ca) (Ti, Mn)O₃ asits main component, that is, when Ca is present as a solid solution atBa sites, the action of suppressing the local grain growth is furtherenhanced, and the reliability is further improved. When the Ca contentratio is 15 mol % or less with respect to all of (Ba, Ca) sites, thelifetime characteristic can be further improved.

In order to produce a raw material for the dielectric ceramic, a Ba(Ti,Mn)O₃ or (Ba, Ca) (Ti, Mn)O₃ based main component powder is firstproduced. For example, a solid-phase synthesis method is applied in sucha way that compound powders containing constituent elements for the maincomponent, such as powders of oxides, carbides, chlorides, and metallicorganic compounds, are mixed at predetermined ratios and calcined. Thegrain diameters of the obtained main component powder are controlled bycontrolling, for example, the calcination temperature. It is to be notedthat a hydrothermal synthesis method or a hydrolysis method may beapplied instead of the solid-phase synthesis method.

On the other hand, compound powders containing each of R, M and Siaccessory components, such as powders of oxides, carbides, chlorides,and metallic organic compounds, are prepared. Then, these accessorycomponent powders are mixed with the main component powder atpredetermined ratios, thereby giving a raw material powder for thedielectric ceramic.

In order to manufacture the laminated ceramic capacitor 1, thedielectric ceramic raw material powder obtained as described above isused to produce a ceramic slurry, ceramic green sheets are formed withthe ceramic slurry, a conductive paste is applied to the sheets, andmultiple ceramic green sheets are stacked, thereby forming a rawlaminate to serve as the capacitor main body 5, and a step of firing theraw laminate is carried out. In this step of firing the raw laminate,the dielectric ceramic raw material powder blended as described above isfired, thereby forming the dielectric ceramic layers 2 composed of thesintered dielectric ceramic.

While, for example, the dielectric ceramic raw material powder, abinder, and an organic solvent are mixed with balls in a ball mill inorder to produce the ceramic slurry, the solid solution region with Rand/or M present therein in the main component grains of the sintereddielectric ceramic, that is, the ratio of the area of the R/M region,can be controlled by adjusting the diameters of the milling balls usedin this step. Of course, methods other than the control of the balldiameters, for example, a method of adjusting the mixing time may alsobe used in order to control the ratio of the area of the R/M region.

Experimental examples carried out in accordance with the invention willbe described below.

Experimental Example 1

In Experimental Example 1, dielectric ceramics containing Ba(Ti, Mn)O₃as a main component and having varied areas of the R/M region wereevaluated.

(A) Production of Ceramic Raw Material

First, respective powders of fine BaCO₃, TiO₂, and MnCO₃ were preparedas starting materials for the main component, weighed to provide aBa(Ti_(0.995)Mn_(0.005))O₃ composition, and mixed with water as a mediumin a ball mill for 8 hours. Then, evaporative drying was carried out,and calcination was carried out at a temperature of 1100° C. for 2hours, thereby giving a main component powder.

Next, respective powders of Y₂O₃, V₂O₅ and SiO₂ to serve as accessorycomponents were prepared, and weighed so that 1.0 part by mol of Y as R,0.25 parts by mol of V as M and 1.5 parts by mol of Si were present withrespect to 100 parts by mol of the main component and blended with themain component powder, followed by mixing with water as a medium in aball mill for 24 hours. Then, evaporative drying was carried out,thereby giving a dielectric ceramic raw material powder.

(B) Production of Laminated Ceramic Capacitor

To the ceramic raw material powder, a polyvinyl butyral based binder andethanol were added, followed by wet mixing in a ball mill for 16 hoursto produce a ceramic slurry. In this step of mixing in a wet manner inthe ball mill, the balls used were changed to have diameters of 2 mm,1.5 mm, 1 mm, 0.8 mm, 0.6 mm, 0.5 mm, and 0.3 mm, respectively, forsamples 101, 102, 103, 104, 105, 106, and 107, thereby changing theratio of the area of the region with R (=Y) and/or M (=V) therein inmain component grains of a sintered dielectric ceramic obtained in asubsequent firing step, that is, the “Ratio of Area of R/M region” asshown in Table 1.

Next, this ceramic slurry was formed into the shape of a sheet by a lipmethod, thereby creating ceramic green sheets.

Next, a conductive paste mainly containing Ni was screen-printed on theceramic green sheets to form conductive paste films to serve as internalelectrodes.

The multiple ceramic green sheets with the conductive paste films formedthem were then stacked so that the drawn ends of the conductive pastefilms were alternately arranged, thereby giving a raw laminate to serveas a capacitor main body.

Next, the raw laminate was heated to a temperature of 300° C. in an N₂atmosphere to burn out the binder, and then fired at a temperature of1200° C. for 2 hours in a reducing atmosphere composed of an H₂—N₂—H₂Ogas with an oxygen partial pressure of 10⁻¹⁰ MPa, thereby giving asintered capacitor main body.

Next, a Cu paste containing B₂O₃—Li₂O—SiO₂—BaO based glass frit wasapplied on the opposite end surfaces of the sintered capacitor mainbody, and fired at a temperature of 800° C. in an N₂ atmosphere to formexternal electrodes electrically connected to the internal electrodes,and thereby form a laminated ceramic capacitor samples.

The thus obtained laminated ceramic capacitors had outer dimensions of2.0 mm in length, 1.2 mm in width, and 1.0 mm in thickness, and thedielectric ceramic layers interposed between the internal electrodes hada thickness of 1.0 μm. The number of the effective dielectric ceramiclayers was 100, whereas the area of the internal electrode opposed perceramic layer was 1.4 mm².

(C) Structural Analysis and Characterization of Ceramic

For the laminated ceramic capacitors thus obtained, the ceramicstructure was observed and analyzed on a cross section of the dielectricceramic layer. In the observation and analysis, the EDX element mappinganalysis in accordance with a STEM mode was carried out in a field ofview including approximately 20 grains to calculate the ratio of thesolid solution area for the Y (=R) and/or V (=M) component as asubsequently added accessory component in the grains, and to obtain theaverage value for the ratio (i.e., the percentage) of the solid solutionarea in the field of view. The results are shown in the column of “Ratioof Area of R/M region” in Table 1. It is to be noted that in the mappinganalysis, the probe diameter was 2 nm, whereas the accelerating voltagewas 200 kV.

In addition, a high temperature load life test was carried out on thelaminated ceramic capacitors thus obtained. In the high temperature loadlife test, a direct current voltage of 12 V (with an electric fieldintensity of 12 kV/mm) was applied to 100 samples at a temperature of125° C., and a sample was regarded as defective when the insulationresistance value was deceased to 100 kΩ or less before a lapse of 1000hours or 2000 hours, thereby giving the number of defectives. Theresults are shown in the column of “Number of Defectives in HighTemperature Load Life Test” in Table 1.

TABLE 1 Number of Defectives in High Sample Ratio of Area TemperatureLoad Life Test Number of R/M region 1000 hours 2000 hours 101 0 0/1000/100 102 3.5 0/100 0/100 103 10 0/100 0/100 104 12 1/100 2/100 105 193/100 4/100 106 22 5/100 6/100 107 61 7/100 9/100

As can be seen from Table 1, for samples 101 to 103 which had a “Ratioof Area of R/M region” of 10% or less, no detectives were formed in thehigh temperature load life test, not only after a lapse of 1000 hoursbut also after a lapse of 2000 hours.

On the other hand, for samples 104 to 107 having a “Ratio of Area of R/Mregion” over 10%, defective(s) were present after a lapse of 1000 hoursin the high temperature load life test.

It is determined from these results that favorable reliability can beobtained when the main component is Ba(Ti, Mn)O₃ and the “Ratio of Areaof R/M region” is 10% or less.

Experimental Example 2

In Experimental Example 2, a dielectric ceramic was evaluated containingBa(Ti, Mn)O₃ as a main component as in the case of Experimental Example1 with the Mn content ratio being varied.

(A) Production of Ceramic Raw Material

A dielectric ceramic raw material powder was obtained in the same way asin the case of Experimental Example 1, expect that the composition ofBa(Ti_(1-x/100)Mn_(X/100))O₃ as a main component powder was adjusted sothat the content ratio x of Mn at (Ti, Mn) sites had values shown in thecolumn “x” in Table 2.

(B) Production of Laminated Ceramic Capacitor

The dielectric ceramic raw material powder was used to manufacturelaminated ceramic capacitors in the same way as in the case ofExperimental Example 1. It is to be noted that in the step of wet mixingin a ball mill, balls 1.5 mm in diameter were used to mix the powdersfor 16 hours, as in the case of sample 102 in Experimental Example 1.

(C) Structural Analysis and Characterization of Ceramic

The ceramic structure analysis carried out in the same way as in thecase of Experimental Example 1 resulted in the “Ratio of Area of R/Mregion” being around 3.5% for all of samples 201 to 208.

In addition, the high temperature load life test was carried out in thesame way as in the case of Experimental Example 1. The results are shownin the column of “Number of Defectives in High Temperature Load LifeTest” in Table 2.

TABLE 2 Number of Defectives in High Sample Temperature Load Life TestNo. x 1000 hours 2000 hours 201 0.55 0/100 0/100 202 0.64 0/100 0/100203 0.70 0/100 0/100 204 0.32 0/100 0/100 205 0.01 0/100 0/100 206 1.000/100 0/100 207 1.10 0/100 2/100 208 1.30 0/100 3/100

As can be seen from Table 2, no detectives were formed in the hightemperature load life test for samples 201 to 206 with the content ratio“x” of Mn in the range of 0.01 to 1.0, not only after a lapse of 1000hours but also after a lapse of 2000 hours.

On the other hand, defectives were present after a lapse of 2000 hoursin the high temperature load life test for samples 207 and 208 with acontent ratio “x” of Mn, outside the range of 0.01 to 1.0, although nodefectives were present after a lapse of 1000 hours.

It is determined from these results that higher reliability can beobtained when the Mn content ratio “x” falls within the range of 0.01 to1.0.

Experimental Example 3

In Experimental Example 3, the influences of the impurities wereevaluated while using Ba(Ti, Mn)O₃ as a main component in the same wayas in the case of Experimental Example 1.

In the process of manufacturing a laminated ceramic capacitor such asthe production of the raw material, there is a possibility that Sr, Zr,Hf, Zn, Na, Ag, Pd, Ni, and the like are introduced as impurities intothe dielectric ceramic, and present in crystal grains and at crystalgrain boundaries between the crystal grains. In addition, there is apossibility that the component of internal electrodes is diffused andpresent in crystal grains of the dielectric ceramic and at crystal grainboundaries between the crystal grains, for example, during the step offiring a laminated ceramic capacitor. Experimental Example 3 is intendedto evaluate the influences of these impurities.

(A) Production of Ceramic Raw Material

A dielectric ceramic raw material powder was obtained in the same way asin the case of Experimental Example 1, expect that impurity componentsshown in Table 3 were added to 100 parts by mol of the dielectricceramic raw material obtained in Experimental Example 1, so as toprovide the content amounts shown in Table 3.

(B) Production of Laminated Ceramic Capacitor

The dielectric ceramic raw material powder was used to manufacturelaminated ceramic capacitor samples in the same way as in the case ofExperimental Example 1. It is to be noted that in the step of mixing ina wet manner in a ball mill, 1.5 mm diameter balls were used to mix thepowders for 16 hours, as in the case of sample 102 in ExperimentalExample 1.

(C) Structural Analysis and Characterization of Ceramic

The ceramic structure analysis carried out in the same way as in thecase of Experimental Example 1 resulted in the “Ratio of Area of R/Mregion” of around 3.5% for all of samples 301 to 310.

In addition, the high temperature load life test was carried out in thesame way as in the case of Experimental Example 1. The results are shownin the column of “Number of Defectives in High Temperature Load LifeTest” in Table 3.

TABLE 3 Number of Defectives in Impurity Components High TemperatureLoad Content Life Test Sample (Parts by 1000 2000 Number Details Mol)hours hours 301 0.4Hf, 0.1Ag 0.50 0/100 0/100 302 0.25Sr, 0.02Zn 0.270/100 0/100 303 0.1Zr, 0.07Zr, 0.01Ag 0.18 0/100 0/100 304 0.5Zr,0.05Ni, 0.1Zn 0.65 0/100 0/100 305 0.2Zr, 0.1Na 0.30 0/100 0/100 3060.5Ni, 0.02Hf, 0.02Ag 0.54 0/100 0/100 307 0.4Pd, 0.01Zn, 0.03Na 0.440/100 0/100 308 5.0Ni 5.00 0/100 0/100 309 1.2Ag, 1.5Zr 4.30 0/100 0/100310 1.8Ni, 0.1Zr 1.90 0/100 0/100

As can be seen from Table 3, no detectives were present in each ofsamples 301 to 310 containing impurities in the high temperature loadlife test, not only after a lapse of 1000 hours but also after a lapseof 2000 hours, and the samples exhibited excellent reliability.

Experimental Example 4

Experimental Example 4 corresponds to Experimental Example 1. The maincomponent was Ba(Ti, Mn)O₃ in Experimental Example 1, whereas the maincomponent is (Ba, Ca) (Ti, Mn)O₃ in Experimental Example 4.

(A) Production of Ceramic Raw Material

First, respective fine powders of BaCO₃, CaCO₃, TiO₂, and MnCO₃ wereprepared as starting materials for the main component, weighed toprovide (Ba_(0.99)Ca_(0.01))(Ti_(0.995)Mn_(0.005))O₃, and mixed withwater as a medium in a ball mill for 8 hours. Then, evaporative dryingwas carried out, and calcination was carried out at a temperature of1100° C. for 2 hours, thereby giving a main component powder.

Next, respective powders of Y₂O₃, V₂O₅ and SiO₂ to serve as accessorycomponents were prepared, and weighed so that 1.0 part by mol of Y, 0.25parts by mol of V and 1.5 parts by mol of Si were present with respectto 100 parts by mol of the main component and blended with the maincomponent powder, followed by mixing with water as a medium in a ballmill for 24 hours. Then, evaporative drying was carried out, therebygiving a dielectric ceramic raw material powder.

(B) Production of Laminated Ceramic Capacitor

To the ceramic raw material powder, a polyvinyl butyral based binder andethanol were added, followed by wet mixing in a ball mill for 16 hoursto produce a ceramic slurry. In this step of mixing in a wet manner inthe ball mill for 16 hours, the balls used were changed to havediameters of 2 mm, 1.5 mm, 1 mm, 0.8 mm, 0.6 mm, 0.5 mm, and 0.3 mm,respectively, for samples 401, 402, 403, 404, 405, 406, and 407, therebychanging the “Ratio of Area of R/M region” in main component grains of asintered dielectric ceramic obtained in a subsequent firing step, asshown in Table 4.

Then, the same steps as in the case of Experimental Example 1 werecarried out to obtain laminated ceramic capacitors as samples.

(C) Structural Analysis and Characterization of Ceramic

For the laminated ceramic capacitors obtained, the “Ratio of Area of R/Mregion” was obtained in the same way as in the case of ExperimentalExample 1. The results are shown in Table 4.

In addition, a high temperature load life test was carried out on thelaminated ceramic capacitors obtained in the same way as in the case ofExperimental Example 1. It is to be noted that the laminated ceramiccapacitors were evaluated after a lapse of 3000 hours in addition toafter a lapse of 1000 hours and after a lapse of 2000 hours inExperimental Example 4. The results are shown in the column of “Numberof Defectives in High Temperature Load Life Test” in Table 4.

TABLE 4 Number of Defectives in High Sample Ratio of Area TemperatureLoad Life Test Number of R/M region 1000 hours 2000 hours 3000 hours 4010 0/100 0/100 0/100 402 3.4 0/100 0/100 0/100 403 10 0/100 0/100 0/100404 12.1 1/100 1/100 3/100 405 16.9 1/100 2/100 4/100 406 21.3 1/1005/100 6/100 407 54.0 1/100 10/100  15/100 

As can be seen from Table 4, no detective was present in the hightemperature load life test, not only after a lapse of 1000 hours andafter a lapse of 2000 hours but also after a lapse of 3000 hours, forsamples 401 to 403 with the “Ratio of Area of R/M region” of 10% orless.

On the other hand, samples 404 to 407 had a “Ratio of Area of R/Mregion” of over 10%, and defectives were present after a lapse of 1000hours in the high temperature load life test.

It is determined from these results that favorable reliability can beobtained when the main component is (Ba, Ca) (Ti, Mn)O₃ and when the“Ratio of Area of R/M region” is 10% or less.

Experimental Example 5

In Experimental Example 5, a dielectric ceramic was evaluated containing(Ba, Ca) (Ti, Mn)O₃ as a main component as in the case of ExperimentalExample 4 in which the Ca content ratio and Mn content ratio werevaried.

(A) Production of Ceramic Raw Material

A dielectric ceramic raw material powder was obtained in the same way asin the case of Experimental Example 4, expect that the composition of(Ba_(1-x/100)Ca_(x/100))(Ti_(1-y/100)Mn_(y/100))O₃ as a main componentpowder was adjusted so that the content ratio x of Ca at (Ba, Ca) siteshad values shown in the column “x” in Table 5, and the content ratio yof Mn at (Ti, Mn) sites had values shown in the column “y” in Table 5.

(B) Production of Laminated Ceramic Capacitor

The dielectric ceramic raw material powder was used to manufacturelaminated ceramic capacitor samples in the same way as in the case ofExperimental Example 4. It is to be noted that in the step of mixing ina wet manner in a ball mill, balls 1.5 mm in diameter were used to mixthe powders for 16 hours, as in the case of sample 402 in ExperimentalExample 4.

(C) Structural Analysis and Characterization of Ceramic

The ceramic structure analysis carried out in the same way as in thecase of Experimental Example 4 resulted in the “Ratio of Area of R/Mregion” of around 3.5% for all of samples 501 to 508.

In addition, the high temperature load life test was carried out in thesame way as in the case of Experimental Example 4. The results are shownin the column of “Number of Defectives in High Temperature Load LifeTest” in Table 5.

TABLE 5 Number of Defectives in High Temperature Load Life Test Sample1000 2000 3000 Number x y hours hours hours 501 1.00 0.50 0/100 0/1000/100 502 2.40 0.70 0/100 0/100 0/100 503 6.40 0.64 0/100 0/100 0/100504 0.01 0.90 0/100 0/100 0/100 505 15.0 0.70 0/100 0/100 0/100 506 16.20.50 0/100 0/100 2/100 507 4.10 0.01 0/100 0/100 0/100 508 9.50 1.000/100 0/100 0/100 509 0.60 1.10 0/100 0/100 1/100 510 15.5 1.30 0/1002/100 3/100

As can be seen from Table 5, samples 501 to 505, 507 and 508 had acontent ratio “x” of Ca of 15 or less, and a content ratio “y” of Mn inthe range of 0.01 to 1.0. No detective was present in the hightemperature load life test, not only after a lapse of 1000 hours butalso after a lapse of 2000 hours and further after a lapse of 3000hours.

On the other hand, sample 506 with the content ratio “x” of Ca over 15,and sample 509 with the content ratio “y” of Mn outside the range of0.01 to 1.0, had no defectives after a lapse of 1000 hours or after alapse of 2000 hours, but defectives were present after a lapse of 3000hours in the high temperature load life test. In addition, sample 510with the content ratio “x” of Ca over 15, and the content ratio “y” ofMn outside the range of 0.01 to 1.0, had defectives after a lapse of2000 hours and after a lapse of 3000 hours in the high temperature loadlife test, although no defective was present after a lapse of 1000hours.

It is determined from these results that higher reliability can beobtained when the Ca content ratio “x” is 15 or less, and when the Mncontent ratio “y” falls within the range of 0.01 to 1.0.

Experimental Example 6

In Experimental Example 6, the influences of the impurities wereevaluated while using (Ba, Ca) (Ti, Mn)O₃ as a main component in thesame way as in the case of Experimental Example 4. Experimental Example6 corresponds to Experimental Example 3 described above.

(A) Production of Ceramic Raw Material

A dielectric ceramic raw material powder was obtained in the same way asin the case of Experimental Example 4, expect that impurity componentsshown in Table 6 were added to 100 parts by mol of the dielectricceramic raw material obtained in Experimental Example 4, so as toprovide the content ratios shown in Table 6.

(B) Production of Laminated Ceramic Capacitor

The dielectric ceramic raw material powder was used to manufacturelaminated ceramic capacitors as each sample in the same way as in thecase of Experimental Example 4. It is to be noted that in the step ofwet mixing in a ball mill, 1.5 mm diameter balls were used to mix thepowders for 16 hours, as in the case of sample 402 in ExperimentalExample 4.

(C) Structural Analysis and Characterization of Ceramic

The ceramic structure analysis carried out in the same way as in thecase of Experimental Example 4 resulted in the “Ratio of Area of R/Mregion” of around 3.5% for all of samples 601 to 610.

In addition, the high temperature load life test was carried out in thesame way as in the case of Experimental Example 4. The results are shownin the column of “Number of Defectives in High Temperature Load LifeTest” in Table 6.

TABLE 6 Number of Defectives in High Temperature Impurity ComponentsLoad Life Test Sample Content 1000 2000 3000 Number Details (Parts byMol) hours hours hours 601 0.4Hf, 0.1Ag 0.50 0/100 0/100 0/100 6020.25Sr, 0.02Zn 0.27 0/100 0/100 0/100 603 0.1Zr, 0.07Zr, 0.01Ag 0.180/100 0/100 0/100 604 0.5Zr, 0.05Ni, 0.1Zn 0.65 0/100 0/100 0/100 6050.2Zr, 0.1Na 0.30 0/100 0/100 0/100 606 0.5Ni, 0.02Hf, 0.02Ag 0.54 0/1000/100 0/100 607 0.4Pd, 0.01Zn, 0.03Na 0.44 0/100 0/100 0/100 608 5.0Ni5.00 0/100 0/100 0/100 609 1.2Ag, 1.5Zr 4.30 0/100 0/100 0/100 6101.8Ni, 0.1Zr 1.90 0/100 0/100 0/100

As can be seen from Table 6, no detective was present in the hightemperature load life test for each of samples 601 to 610 containingimpurities, not only after a lapse of 1000 hours but also after a lapseof 2000 hours and further after a lapse of 3000 hours, and the samplesexhibited excellent reliability.

While Y was used for an accessory component R whereas V was used as Mfor an accessory component in the experimental examples described above,it has been confirmed that substantially the same results are obtainedeven when La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, or Luother than Y is used as R or when Fe, Co, W, Cr, Mo, Cu, Al, or Mg otherthan V is used as M.

1. A dielectric ceramic comprising: a main component which is one ofBa(Ti, Mn)O₃ and (Ba, Ca)(Ti, Mn)O₃; and R, M and Si as accessorycomponents, where R is at least one member selected from the groupconsisting of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu,and Y, and M is at least one member selected from the group consistingof Fe, Co, V, W, Cr, Mo, Cu, Al, and Mg, wherein the area of a region inwhich at least one of R and M is present is 10% or less on average of across section of each main component grain.
 2. The dielectric ceramicaccording to claim 1, wherein the Mn content is 0.01 to 1 mol % withrespect to all of (Ti, Mn) sites.
 3. The dielectric ceramic according toclaim 2, wherein the Mn content is up to 0.9 mol % with respect to allof (Ti, Mn) sites.
 4. The dielectric ceramic according to claim 3,wherein the Mn content is up to 0.7 mol % with respect to all of (Ti,Mn) sites.
 5. The dielectric ceramic according to claim 2, wherein themain component is Ba(Ti, Mn)O₃.
 6. The dielectric ceramic according toclaim 5, wherein R comprises Y and M comprises V.
 7. The dielectricceramic according to claim 2, wherein the main component is (Ba, Ca)(Ti, Mn)O₃.
 8. The dielectric ceramic according to claim 7, wherein theCa content is 15 mol % or less with respect to all of (Ba, Ca) sites. 9.The dielectric ceramic according to claim 8, wherein the Ca content is0.6 to 3.4 mol % with respect to all of (Ba, Ca) sites.
 10. Thedielectric ceramic according to claim 8, wherein R comprises Y and Mcomprises V.
 11. A laminated ceramic capacitor comprising: a capacitormain body comprising a plurality of stacked dielectric ceramic layersand a plurality of internal electrodes disposed at different interfacesbetween the dielectric ceramic layers; and two external electrodesdisposed at positions different from each other on an external surfaceof the capacitor main body and electrically connected to differentinternal electrodes, wherein the dielectric ceramic layers comprise adielectric ceramic according to claim
 10. 12. A laminated ceramiccapacitor comprising: a capacitor main body comprising a plurality ofstacked dielectric ceramic layers and a plurality of internal electrodesdisposed at different interfaces between the dielectric ceramic layers;and two external electrodes disposed at positions different from eachother on an external surface of the capacitor main body and electricallyconnected to different internal electrodes, wherein the dielectricceramic layers comprise a dielectric ceramic according to claim
 9. 13. Alaminated ceramic capacitor comprising: a capacitor main body comprisinga plurality of stacked dielectric ceramic layers and a plurality ofinternal electrodes disposed at different interfaces between thedielectric ceramic layers; and two external electrodes disposed atpositions different from each other on an external surface of thecapacitor main body and electrically connected to different internalelectrodes, wherein the dielectric ceramic layers comprise a dielectricceramic according to claim
 8. 14. A laminated ceramic capacitorcomprising: a capacitor main body comprising a plurality of stackeddielectric ceramic layers and a plurality of internal electrodesdisposed at different interfaces between the dielectric ceramic layers;and two external electrodes disposed at positions different from eachother on an external surface of the capacitor main body and electricallyconnected to different internal electrodes, wherein the dielectricceramic layers comprise a dielectric ceramic according to claim
 7. 15. Alaminated ceramic capacitor comprising: a capacitor main body comprisinga plurality of stacked dielectric ceramic layers and a plurality ofinternal electrodes disposed at different interfaces between thedielectric ceramic layers; and two external electrodes disposed atpositions different from each other on an external surface of thecapacitor main body and electrically connected to different internalelectrodes, wherein the dielectric ceramic layers comprise a dielectricceramic according to claim
 6. 16. A laminated ceramic capacitorcomprising: a capacitor main body comprising a plurality of stackeddielectric ceramic layers and a plurality of internal electrodesdisposed at different interfaces between the dielectric ceramic layers;and two external electrodes disposed at positions different from eachother on an external surface of the capacitor main body and electricallyconnected to different internal electrodes, wherein the dielectricceramic layers comprise a dielectric ceramic according to claim
 5. 17. Alaminated ceramic capacitor comprising: a capacitor main body comprisinga plurality of stacked dielectric ceramic layers and a plurality ofinternal electrodes disposed at different interfaces between thedielectric ceramic layers; and two external electrodes disposed atpositions different from each other on an external surface of thecapacitor main body and electrically connected to different internalelectrodes, wherein the dielectric ceramic layers comprise a dielectricceramic according to claim
 4. 18. A laminated ceramic capacitorcomprising: a capacitor main body comprising a plurality of stackeddielectric ceramic layers and a plurality of internal electrodesdisposed at different interfaces between the dielectric ceramic layers;and two external electrodes disposed at positions different from eachother on an external surface of the capacitor main body and electricallyconnected to different internal electrodes, wherein the dielectricceramic layers comprise a dielectric ceramic according to claim
 3. 19. Alaminated ceramic capacitor comprising: a capacitor main body comprisinga plurality of stacked dielectric ceramic layers and a plurality ofinternal electrodes disposed at different interfaces between thedielectric ceramic layers; and two external electrodes disposed atpositions different from each other on an external surface of thecapacitor main body and electrically connected to different internalelectrodes, wherein the dielectric ceramic layers comprise a dielectricceramic according to claim
 2. 20. A laminated ceramic capacitorcomprising: a capacitor main body comprising a plurality of stackeddielectric ceramic layers and a plurality of internal electrodesdisposed at different interfaces between the dielectric ceramic layers;and two external electrodes disposed at positions different from eachother on an external surface of the capacitor main body and electricallyconnected to different internal electrodes, wherein the dielectricceramic layers comprise a dielectric ceramic according to claim 1.